EP0543505A1 - Optischer Kopf mit Mehrfachstrahl - Google Patents

Optischer Kopf mit Mehrfachstrahl Download PDF

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Publication number
EP0543505A1
EP0543505A1 EP92309568A EP92309568A EP0543505A1 EP 0543505 A1 EP0543505 A1 EP 0543505A1 EP 92309568 A EP92309568 A EP 92309568A EP 92309568 A EP92309568 A EP 92309568A EP 0543505 A1 EP0543505 A1 EP 0543505A1
Authority
EP
European Patent Office
Prior art keywords
light emitting
emitting points
light
optical head
col
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP92309568A
Other languages
English (en)
French (fr)
Other versions
EP0543505B1 (de
Inventor
Koichiro C/O Canon Kabushiki Kaisha Nishikawa
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Canon Inc
Original Assignee
Canon Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Canon Inc filed Critical Canon Inc
Publication of EP0543505A1 publication Critical patent/EP0543505A1/de
Application granted granted Critical
Publication of EP0543505B1 publication Critical patent/EP0543505B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
    • G11B7/127—Lasers; Multiple laser arrays
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
    • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
    • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
    • G11B11/10532—Heads
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor

Definitions

  • This invention relates to an optical head for use in an optical information recording-reproducing apparatus such as a magneto-optical disk apparatus, and particularly to an optical head using a light source having a plurality of light emitting points.
  • the optical head of the present invention can be applied as an optical head for effecting at least two of the erasing, recording and reproduction of information at a time.
  • optical heads capable of effecting erasing and recording or recording and reproduction at a time by the use of a plurality of beams.
  • the outward optical system of it is such as shown in the block diagram of Figure 1 of the accompanying drawings.
  • two laser beams emitted from a monolithic semiconductor laser array 5 having two light emitting points are imaged as light spots for recording and reproduction on a magneto-optical disk 12 which is an optical information recording medium through a collimator lens 8, a beam splitter 23 and an objective lens 11, and recording and reproduction can be accomplished at a time by these two spots.
  • the spacing between the light emitting points thereof is generally of the order of 100 ⁇ m or more in order to avoid thermal interference and electrical interference between the light emitting points.
  • the reference numeral 1 designates a track of radius a having a point 2 as its center.
  • Two spots 3 and 4 are spaced apart by a distance L from each other, and both of them are on the track 1.
  • the track becomes eccentric, for example, when the track 1 is rotated by an angle ⁇ about the spot 3 and moves to 1′, the center of the track moves to 2′ and the position on the track which corresponds to the spot 4 moves to 4′.
  • the spacing between the position 2 and the position 2′ corresponds to the amount of eccentricity W
  • the spacing between the position 4 and the position 4′ is the amount of relative track deviation ⁇ T.
  • L 38 mm
  • ⁇ T ⁇ 0.13 ⁇ m and thus, in the prior-art optical head as described above, there is caused relative track deviation of 0.13 ⁇ m or more.
  • Two laser beams emitted from the semiconductor laser chips 101 and 102 are collimated by a collimator lens 8, are transmitted through a half wavelength plate 24 and a beam splitter 23 along substantially the same optical path, are reflected by a mirror 10 and are stopped down as spots 3 and 4 for recording and reproduction, respectively, on a magneto-optical disk 12 by an objective lens 11. Since the light source is of an array construction comprising semiconductor laser chips opposed to each other, the laser beams emitted from the semiconductor laser chips become s-polarized lights relative to the beam splitter 23. Because of the characteristic of the beam splitter 23, s-polarized lights are inconvenient and therefore, the s-polarized lights are converted into p-polarized lights by the half wavelength plate 24.
  • the spacing d between the light emitting points is 27 ⁇ m
  • the spacing L between the spots is of the order of 10.3 ⁇ m
  • the corresponding amount of relative track deviation ⁇ T is 0.035 ⁇ m when eccentricity is 100 ⁇ m.
  • the allowable amount of track deviation is of the order of 0.1 ⁇ m.
  • the order of 0.07 ⁇ m or less is desired as the amount of relative track deviation ⁇ T. That is, the order of 21 ⁇ m or less is desired as the spacing L between the spots.
  • the spacing between the light emitting points is made small by the construction in which the laser chips are opposed to each other, thereby realizing an amount of relative track deviation ⁇ T of 0.07 ⁇ m or less, but the construction in which the laser chips are opposed to each other requires a half wavelength plate, thus resulting in an increase in the number of parts.
  • the fact of being hybrid leads to a construction in which the positions of the two light emitting points are held by the mount member and the spacing between the light emitting points is liable to change and therefore, as compared with the case of being monolithic, there is a problem in respect of the reliability in the light source portion.
  • a plural-beam optical head having a monolithic semiconductor laser array having a plurality of light emitting points, a collimator lens for collimating a plurality of laser beams emitted from said plurality of light emitting points, and an objective lens for imaging said plurality of laser beams on an optical information recording medium, characterized in that provision is made of means for expanding the diameters of said plurality of laser beams in the direction of arrangement of said light emitting points, and the following condition is satisfied: (d ⁇ f0)/(f col ⁇ m) ⁇ 20 [ ⁇ m], where d is the maximum spacing between adjacent ones of said plurality of light emitting points, f col is the focal length of said collimator lens, f0 is the focal length of said objective lens, and m is the expansion magnification of said means for expanding the diameters of said laser beams.
  • the plural-beam optical head of the present invention uses a monolithic semiconductor laser array and therefore can secure high reliability as compared with one using a hybrid semiconductor laser array. Also, in the present embodiment, use is made of means for expanding the di:meters of the plurality of laser beams in the direction of arrangement of the light emitting points of the monolithic semiconductor laser array and therefore, by suitably setting the focal length of the collimator lens, the focal length of the objective lens and the expansion magnification of the means for expanding the diameters of the laser beams, the spacing between light spots on the optical information recording medium can be made sufficiently small even if the spacing between the light emitting points of the laser array is great and thus, there can be constructed an optical head in which the amount of track deviation by the eccentricity or the like of information tracks is sufficiently small.
  • Figure 1 is a schematic diagram showing the outward optical system of an optical head according to the prior art.
  • Figure 2 illustrates the manner in which relative track deviation occurs between two spots.
  • Figure 3 is a schematic diagram showing the outward optical system of an optical head according to the prior art.
  • Figure 4 is a plan view showing the construction of the optical head of the present invention.
  • Figure 5 is a side view of the optical head of Figure 4.
  • Figure 6 illustrate beams transmitted through a beam shaping prism.
  • Figure 4 is a plan view showing the construction of the optical head of the present invention
  • Figure 5 is a side view thereof.
  • the present embodiment is a two-beam optical head.
  • a monolithic semiconductor laser array 5 has light emitting points 6 and 7. Both of these light emitting points are 830 nm in wavelength and 30 mW in output, and the spacing d therebetween is 100 ⁇ m.
  • Two beams emitted from the light emitting points 6 and 7 are collimated by a collimator lens 8, are transmitted through a beam splitter 9 with a beam shaping portion, are reflected by a mirror 10 and are stopped down as a spot 3 for recording and a spot 4 for reproduction on the track 13 of a magneto-optical disk 12 by an objective lens 11. Recording and reproduction can be accomplished at a time by these two spots.
  • the reflected beams of the two spots 3 and 4 are again collimated by the objective lens 11, are reflected by the mirror 10, are reflected by the beam splitter 9 with a beam shaping portion, and enter a beam splitter 15.
  • the beams transmitted through the beam splitter 15 are directed to a servo error detection system comprising a convex lens 16, a cylindrical lens 17 and a servo sensor 18.
  • the beams reflected by the beam splitter 15 are directed to a signal detection system comprising a double-refractive crystal 19, a convex lens 20 and an RF sensor 21.
  • the angle ⁇ formed between the two beams collimated by the collimator lens 8 is expressed as ⁇ ⁇ d/f col , where f col is the focal length of the collimator lens.
  • the two beams forming an angle ( ⁇ /m) therebetween after having passed through the shaping prism are imaged as two spots having a spot spacing L therebetween.
  • the focal length of the objective lens is f0
  • L is expressed as L ⁇ f0 ⁇ ( ⁇ /m).
  • d 100 ⁇ m
  • f col 8 mm
  • m 2.4
  • f0 3.8 mm
  • the spot spacing L is about 20 ⁇ m.
  • the combined focal length is about 45 mm and the diameter of the spots on the servo sensor 18 is set as about 100 ⁇ m ⁇ , whereby the spacing between the spots on said servo sensor 18 is of the order of 230 ⁇ m from 45 x ( ⁇ /m) and therefore, the spots are completely spatially separated on the servo sensor 18.
  • the beam shaping ratio m of the beam splitter 9 with a beam shaping portion is 2.4, but the value of said beam shaping ratio may be otherwise, e.g. may be set within the range of 1.4 - 3.5.
  • Examples of the combination of the focal length f col of the collimator lens, the focal length f0 of the objective lens and the spacing d between the two light emitting points in that case will be shown in Table 1 below with the values of (d ⁇ f0)/(f col ⁇ m).
  • the optical information recording medium is in the form of a disk
  • the present invention is equally effective when use is made of any other recording medium than the disk-like medium.
  • an optical head which can form on an optical information recording medium a plurality of spots having a narrow spot spacing therebetween by the use of a monolithic semiconductor laser array in which the relative position of a plurality of light emitting points is stable, and in which track deviation occurring from the eccentricity or the like of a disk.

Landscapes

  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Head (AREA)
  • Optical Recording Or Reproduction (AREA)
EP92309568A 1991-10-22 1992-10-20 Optischer Kopf mit Mehrfachstrahl Expired - Lifetime EP0543505B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP30124191 1991-10-22
JP301241/91 1991-10-22
JP3301241A JPH05114159A (ja) 1991-10-22 1991-10-22 複数ビーム光ヘツド

Publications (2)

Publication Number Publication Date
EP0543505A1 true EP0543505A1 (de) 1993-05-26
EP0543505B1 EP0543505B1 (de) 1999-12-22

Family

ID=17894479

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92309568A Expired - Lifetime EP0543505B1 (de) 1991-10-22 1992-10-20 Optischer Kopf mit Mehrfachstrahl

Country Status (4)

Country Link
US (1) US5353274A (de)
EP (1) EP0543505B1 (de)
JP (1) JPH05114159A (de)
DE (1) DE69230461T2 (de)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07129992A (ja) * 1993-11-06 1995-05-19 Asahi Optical Co Ltd 情報記録再生装置
JPH07147020A (ja) * 1993-11-24 1995-06-06 Canon Inc 複数ビーム光ヘッド
GB2300749A (en) * 1995-05-06 1996-11-13 Thomson Multimedia Sa A multiple beam optical disk system
US6031810A (en) * 1996-09-18 2000-02-29 Canon Kabushiki Kaisha Using two laser sources on a magneto-optical recording medium for preventing light intensity shortage
JPH10106040A (ja) * 1996-09-26 1998-04-24 Canon Inc 光学的情報記録媒体および光学的情報記録再生装置
US5995472A (en) * 1997-05-06 1999-11-30 Canon Kabushiki Kaisha Laser beam forming temperature distribution of two peaks on a magneto-optical recording medium
KR100457948B1 (ko) * 2002-02-15 2004-11-18 삼성전기주식회사 광 픽업용 2파장 광원모듈
JP2005216337A (ja) * 2004-01-27 2005-08-11 Canon Inc 光学的情報記録再生装置
US7791986B2 (en) * 2006-03-15 2010-09-07 Canon Kabushiki Kaisha Optical information recording/reproducing apparatus

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0097035A1 (de) * 1982-06-10 1983-12-28 Xerox Corporation System zum Aufzeichnen und Ablesen einer optischen Scheibe
EP0216704A2 (de) * 1985-09-20 1987-04-01 Fujitsu Limited Verfahren und Gerät zur optischen Aufnahme und Wiedergabe
JPH01251330A (ja) * 1987-12-28 1989-10-06 Ricoh Co Ltd マルチビーム光ピックアップ
US4901325A (en) * 1987-03-26 1990-02-13 Hitachi, Ltd. Semiconductor laser device
EP0388760A1 (de) * 1989-03-14 1990-09-26 Fuji Xerox Co., Ltd. Laserdiode und optischer Kopf mit mehreren Strahlen, welcher die Laserdiode verwendet

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4520472A (en) * 1983-02-07 1985-05-28 Rca Corporation Beam expansion and relay optics for laser diode array
EP0147620B1 (de) * 1983-11-22 1991-06-05 Kabushiki Kaisha Toshiba Optischer Kopf
JPS6383931A (ja) * 1986-09-27 1988-04-14 Toshiba Corp 発光素子
US4951274A (en) * 1987-01-23 1990-08-21 Nec Corporation Magneto-optical head capable of separating beams for reading recorded information and servo information by use of one optical element
JP2765839B2 (ja) * 1987-09-11 1998-06-18 株式会社日立製作所 ２ビーム光ヘッド
JPH01138627A (ja) * 1987-11-26 1989-05-31 Ricoh Co Ltd 光デイスク装置
US5105410A (en) * 1987-12-28 1992-04-14 Ricoh Company, Ltd. Multi-beam optical pick-up
US5073888A (en) * 1988-04-21 1991-12-17 Ricoh Company, Ltd. Optical pickup device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0097035A1 (de) * 1982-06-10 1983-12-28 Xerox Corporation System zum Aufzeichnen und Ablesen einer optischen Scheibe
EP0216704A2 (de) * 1985-09-20 1987-04-01 Fujitsu Limited Verfahren und Gerät zur optischen Aufnahme und Wiedergabe
US4901325A (en) * 1987-03-26 1990-02-13 Hitachi, Ltd. Semiconductor laser device
JPH01251330A (ja) * 1987-12-28 1989-10-06 Ricoh Co Ltd マルチビーム光ピックアップ
EP0388760A1 (de) * 1989-03-14 1990-09-26 Fuji Xerox Co., Ltd. Laserdiode und optischer Kopf mit mehreren Strahlen, welcher die Laserdiode verwendet

Also Published As

Publication number Publication date
DE69230461D1 (de) 2000-01-27
JPH05114159A (ja) 1993-05-07
EP0543505B1 (de) 1999-12-22
DE69230461T2 (de) 2000-05-18
US5353274A (en) 1994-10-04

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